Ferrari say they have taken some "innovative" steps in an attempt to close the gap, redesigning the front of their car and power unit layout, but Mercedes enter 2016 as F1's undisputed leading force after back-to-back world titles.

But speaking after the W07 was put through its early laps at Silverstone, Mercedes executive director Lowe acknowledged the likelihood of an increased challenge from their Italian rivals.

"We see Ferrari as our main threat and it remains to be seen how we position ourselves in the weeks to come," Lowe told Sky Sports News HQ.

"Ferrari are a very strong competitor and one we worry about. It keeps us motivated to keep us pushing all the time."

Exclusive pictures of the Mercedes W07 - their new car for the 2016 F1 season

Exclusive pictures of the Mercedes W07 - their new car for the 2016 F1 season

Nico Rosberg was behind the wheel for the W07's initial laps at Silverstone, before handing over to world champion team-mate Lewis Hamilton in the afternoon.

The German is also expecting a more intense battle with Ferrari this year.

"We take our opposition very seriously - especially Ferrari," Rosberg said. "For sure, they are going to be a big threat so we need to keep pushing. Who knows where we are going to be first race?"

With the new Ferrari and Williams cars breaking cover on Friday, and McLaren to follow on Sunday, Lowe admits Mercedes' engineers will already be looking out for something they may have missed in the W07's conception.

"This is a great time of year," he said. "One of the games we are all playing behind the scenes is waiting for those launch photos and our aerodynamicists will pour over those to see if there is something interesting or something we haven't thought of."

Craig Slater catches up with Nico Rosberg at Silverstone

Craig Slater catches up with Nico Rosberg at Silverstone

Although Mercedes' Silverstone shakedown was mainly for filming purposes, and they were were restricted to 100km and running on demonstration tyres, the laps completed would have allowed them to iron out any teething problems with the W07.

However, in what could already be considered an ominous sign for their would-be 2016 rivals, Lowe revealed: "We haven't even taken the engine cover off yet in the whole morning session which is a really good sign of the reliability we've achieved at this point.

"Today is all about filming and making sure we are able to hit the ground running on Monday when we get into the proper testing and see whether there are any major issues that we've overlooked. But so far so good."

The first Barcelona test starts on Monday February 22 and the Sky Sports F1 Digital team will be providing live commentary from dawn until dusk on all four days of both Barcelona tests while Sky Sports News HQ will also deliver live updates from trackside.